Yes activity level is the key to being successful in achieving your weight loss and even fitness goals. The simple truth is the more active you are, the more calories you burn, the more calories you can eat.
Great example, when I was competing in the Olympics I would train twice, sometimes three times a day. I ate around 6,000 to 7,000 calories and wore a 50" suit coat and weighed 205.
I now eat around 2700 calories a day, train once a day 4 to 5 days a week and partly (although very rarely) sit at a desk and weigh 195. Now when I was 205 I was MUCH MUCH larger and carried more muscle than I do now and I am much more active than most people and watch my diet like a hawk, cheating only once per week and I use that term loosely, it really means I only eat more of what I already eat, not that I eat twinkies and ho hos!
So I sense frustration from people, and some clients, when they think they "watch what they eat" and workout 2 to 3 times a week like that is going to cut it. Guess what, I will repeat my statement, I KNOW exaclty how many calories I am taking in daily, workout reguarly and rarely ever eat anything I am not suppose to and it is STILL a daily struggle to maintain my weight.
Until you know exaclty how many calories you are taking in a day you are only going to set yourself up to fail. It is like trying to make a budget without knowing how much money you are spending, sure you may curtail your spending habbits alittle but you are still fying blind. Remember that!